Hydrodynamic axial slide bearing for a generator

ABSTRACT

Hydrodynamic plane thrust bearing ( 26 ) for a generator ( 10 ), preferably operable with a water turbine, with a rotor ( 12 ), a track ring ( 30 ) rotating with the shaft ( 20 ) of the rotor ( 12 ), and a bearing segment ( 32 ) not rotating with the shaft ( 20 ) of the rotor ( 12 ) and supported on a bearing housing ( 24 ), characterized in that the track ring ( 30 ) substantially consists of a plastic matrix with reinforcing fibers embedded therein.

FIELD OF THE INVENTION

[0001] The invention relates to a hydrodynamic plane thrust bearing fora generator for current production, according to the preamble of claim1.

DESCRIPTION OF PRIOR ART

[0002] The bearings occupy a key position in large generators forcurrent production. If the bearing fails, the current production basedon this generator comes to a standstill. Besides the radial bearings forthe shaft, the thrust bearings, above all in vertically operatedgenerators, such as are, for example, used for current production bymeans of water turbines, have to withstand a large load. A very elegantbut expensive possibility is the design of the axial bearing as amagnetic bearing. Another possibility consists of its design as a rollerbearing. However, these bearings are not suitable for diameters ofseveral meters, because of their large dimensions and the associatedrelatively large shape inaccuracy of the individual parts.

[0003] Hydrodynamic plane thrust bearings are the usual constructionalform, in which a track ring is fixed to and rotates with the rotorshaft. This track ring supports the rotor axially against a bearinghousing. The track ring slides on a lubricant film over bearing segmentsarranged in the bearing housing.

[0004] According to EP 1058368A2, FIG. 3, hydrodynamic thrust bearingsare used for shaft mounting, and are constructed as axial journalbearings or as combined journal and double thrust bearings. The bearingmethod is ensured by means of a stable hydrodynamic lubricant film,which is built up by a wedge profile in the lubrication gap. In suchlarge generators for current production, track rings of about 2 m-6 mdiameter are used. At the high rotational speeds used, correspondinglyhigh temperatures occur in the hydrodynamic plane thrust bearings andhave to be withstood by the track ring. Furthermore, the hydrodynamicpressure in the lubrication gap can become so large that even adjoiningmetallic surfaces are permanently deformed. The track rings for suchhydrodynamic plane thrust bearings must therefore have a high stiffnessand strength and also a high heat resistance. Hence they were heretoforemade of steel. So that an immediate breakdown of the bearing does notoccur upon partial lubrication failure of the hydrodynamic plane thrustbearing, the bearing segments are coated with a sliding material suchas, for example, white metal or polytetrafluoroethylene (PTFE). Becauseof the large thermal expansion coefficient of steel, however,deformation of the track ring (curvature of the surface or waveformation) occurs under the high temperatures in the bearing, andrepresents a greater problem, the greater the diameter of the trackring. Due to the unpredictable deformations, large wear phenomena oreven damage can occur in these track rings in the hydrodynamic planethrust bearing. The maintenance cost and inoperative time for changingsingle bearing components are correspondingly large, and reduce theeconomic efficiency of the generator. Moreover, the weight of the steeltrack rings in large generators, such as are used for currentproduction, often already represent a problem in transport and duringmounting at the site.

SUMMARY OF THE INVENTION

[0005] The object of the invention is therefore to provide ahydrodynamic plane thrust bearing of the kind mentioned at thebeginning, having a higher lifetime and loadability and simplermounting, so that the generator is more economical in mounting andoperation.

[0006] This object is attained by a hydrodynamic plane thrust bearingaccording to the preamble of claim 1, in which the track ringsubstantially consists of a plastic matrix with reinforcing fibersembedded therein. Such a plane thrust bearing therefore possesses a highlifetime, because the fiber-reinforced plastic has a smaller expansioncoefficient than steel and the track ring therefore deforms hardly atall. Thus damage due to large deformations of the steel track rings areavoided. Since in addition track rings of fiber-reinforced plasticfurthermore have a much smaller weight than those of steel, bothtransport and mounting are much more easily and cost-effectivelyperformed. Furthermore larger designs of such bearings can beimplemented than is possible with steel track rings.

[0007] It is very favorable to use a fiber-reinforced plastic withcontinuous fibers, since in this manner both more favorable stiffnessvalues and also a smaller expansion coefficient are attained.

[0008] If the track ring is manufactured as a laminate of at least fourlayers of fiber-reinforced plastic with respectively unidirectionallyaligned fibers, and if the angle of the fiber direction of the layers isbetween 0° and 90°, the thermal expansion of the track ring can befurther reduced.

[0009] If an epoxy matrix is chosen as the plastic matrix, anadvantageous heat resistance is ensured.

[0010] It is very advantageous if carbon fibers are used as thereinforcing fibers, since these have a negative thermal expansioncoefficient. If carbon fibers are embedded, laminated into an epoxyresin matrix, a material of almost no thermal expansion and with anincreased specific stiffness can be attained.

[0011] According to the requirements of the respective hydrodynamicplane thrust bearing, a fiber proportion of 50 vol. % to 70 vol. % inthe track ring is very advantageous, since the strength and stiffness ofthe track ring rise with increasing fiber proportion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The subject of the invention is explained in detail hereinafterusing examples of preferred embodiments which are shown in theaccompanying drawings. Purely schematically:

[0013]FIG. 1 shows a sectional diagram of a hydrodynamic plane thrustbearing with a composite material track ring according to the invention;

[0014]FIG. 2 shows a section through a track ring according to theinvention;

[0015]FIG. 3 shows an exemplary exploded diagram of eight successivelayers of the track ring.

[0016] The reference numerals used in the drawings and their meaning aresummarized in the list of reference numerals. Basically the same partsare given the same reference numerals in the Figures. The describedembodiment examples are given as examples of the subject of theinvention and are in no way limitative thereof.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0017]FIG. 1 shows schematically an excerpt of a vertically alignedgenerator 10 driven by a water turbine (not shown). A rotor 12 of thegenerator 10 is shown, with generator poles 14 at the edge of the rotorcrown 16. The rotor crown 16 is connected to the rotor shaft by means ofa rotor hub 18. The rotor shaft can be embodied as one piece or, asshown, by an upper shaft portion 20 and a lower shaft portion 22. Therotor hub 18 likewise connects the upper shaft portion 20 of thegenerator 10 with the lower shaft portion 22, which leads to the turbine(not shown). The lower shaft portion 22 of the turbine is axiallymounted in a bearing housing 24. A hydrodynamic plane thrust bearing 26is arranged between the bearing housing 24 and the rotor 12. Thehydrodynamic plane thrust bearing 26 consists of a rotating track ring30 of a fiber-reinforced plastic matrix and of stationary bearingsegments 32. The bearing segments 32 are embodied so that a wedge-shapedlubricating film can form between the track ring 30 and the bearingsegments 32. These bearing segments 32 are as a rule individual memberswhich can freely turn around a fulcrum 34 supported on the housing wall36 of the bearing housing 24, as indicated by a corresponding doublearrow in FIG. 1. The lubrication gap can be optimally set up in thismanner. The hydrodynamic plane thrust bearing 26 is operated using alubricant 28, usually machine oil. The oil level exceeds the height ofthe lubrication gap between the track ring 30 and the bearing segment32. An individual oil supply to the individual bearing segments 32 isalso conceivable.

[0018]FIG. 2 shows a preferred embodiment of the track ring 30 offiber-reinforced plastic, in section along the rotation axis 38. Thetrack ring 30 is produced as a laminate of plural layers 40 offiber-reinforced plastic, the fibers being carbon fibers withunidirectional alignment in each layer 40. The fibers are embedded in anepoxy matrix. The angle of the alignment of the carbon fibers is changedfrom layer 40 to layer 40. In order to obtain the required thickness ofthe track ring 30, an angle sequence of[[0°/−45°/45°/90°]_(symmetrical)]_(n) repeated with a plurality of times(index “n”).

[0019] The sequence of eight layers 40 with the given angle sequence isshown in FIG. 3 in an exploded diagram. A deformation of the track ringcan be countered by such a symmetrical layer arrangement. The alignmentangle of the fibers can of course vary.

[0020] The track ring can be produced simply and favorably, e.g., by anautoclave method from preformed prepregs. An aperture 42 in the middleof the track ring, required for the shaft 20/22 to pass through thetrack ring 30, can easily be produced by drilling or turning. Requiredstructures in the surface of the track ring 30 can of course likewiseeasily be machined into the surface by milling.

[0021] According to the requirements of the hydrodynamic plane thrustbearing, fibers such as carbon fibers, glass fibers or also polyamidefibers can be used. Instead of an epoxy matrix, other thermallyresistant plastics can also be chosen, such as, for example, Rhodeftalpolyaminoimide (from Vantico). Where this appears necessary, a furthercoating can be applied to the track ring, and is likewise to bepreferably a plastic coating because of better adhesion properties.

[0022] It is of course possible to manufacture not only the track ringbut also the shaft of the fiber-reinforced plastic. Further weight canbe saved thereby.

[0023] A further advantage of the whole construction of the generatorresults when the hydrodynamic plane thrust bearing is combined with aradial guide bearing. The track ring is then used both for the planethrust bearing and for the guide bearing. In this case, the smallerdeformation of the track ring improves the operating behavior of theradial bearing.

Reference List

[0024]10 generator

[0025]12 rotor

[0026]14 generator pole

[0027]16 rotor crown

[0028]18 rotor hub

[0029]20 upper shaft portion

[0030]22 lower shaft portion

[0031]24 bearing housing

[0032]26 hydrodynamic plane thrust bearing

[0033]28 lubricant

[0034]30 track ring

[0035]32 bearing segment

[0036]34 fulcrum

[0037]36 housing wall

[0038]38 rotation axis

[0039]40 layer

[0040]42 aperture

1. Hydrodynamic plane thrust bearing for a generator (10) preferablyoperable by means of a water turbine, with a rotor (12), a track ring(30) rotating with the shaft of the rotor (12) and at least one bearingsegment (32) not rotating with the shaft (20) of the rotor (12) andsupported on a bearing housing (24), wherein the track ring (30)substantially consists of a plastic matrix with reinforcing fibersembedded therein.
 2. Hydrodynamic plane thrust bearing according toclaim 1, wherein continuous fibers are embedded in the plastic matrix.3. Hydrodynamic plane thrust bearing according to claim 2, wherein theplastic matrix is an epoxy matrix.
 4. Hydrodynamic plane thrust bearingaccording to one of claims 1-3, wherein the reinforcing fibers arecarbon fibers.
 5. Hydrodynamic plane thrust bearing according to one ofclaims 1-4, wherein the fiber proportion in the matrix is between 50vol. % and 70 vol. %.
 6. Hydrodynamic plane thrust bearing according toone of claims 1-5, wherein the track ring (30) consists of a laminate ofat least four layers (40) of fiber-reinforced plastic, the fibers ineach layer (40) being unidirectionally aligned and the angle of thefiber alignment of the layers being between 0° and 90°.
 7. Hydrodynamicplane thrust bearing according to claim 6, wherein the layers (40) ofthe laminate have an angle sequence of[[0°/−45°/45°/90°]_(symmetrical)]_(n).